This invention claims priority of a Swiss filed patent application CH P 1651/99 filed Sep. 9, 1999.
The invention concerns devices for illuminating a surgical field of view of a surgical microscope, for example an ophthalmic surgical microscope.
It is known to provide an illumination device for a surgical microscope in which the entire light beam from an illumination optical system associated with a lamp is deflected by a first prism out of a perpendicular to the principal axis of the principal objective of the microscope into an oblique inclination at a small angle with respect to the principal axis, and in which a second portion of the total light beam quantity is cast onto the surgical field approximately parallel to the principal axis. This configuration is used in particular for ophthalmic surgery. In the center of the surgical field, the illumination is approximately parallel to the surgical microscope axis, whereas around that center it radiates at a small angle toward the surgical field. During the surgery, the illumination component at a small angle is usually blocked out by a slide-in stop, so that the surgeon has available only the parallel illumination component. As a result, however, the actual illuminated surgical field is also narrowed down to the diameter of the illumination with the parallel component.
This has in some cases been perceived as a disadvantage in practical use, so that the object of the invention is to achieve an improved blocking-out effect that nevertheless also admits some light for the region at a small angle, so that this region is not completely darkened.
One obvious step toward achieving this is not to place the stop, which is already provided as standard equipment, entirely in front of the prism output, but rather to leave open a small gap for a small amount of light to pass; with some equipment this is in fact done by users. Experiments have revealed, however, that this approach is not satisfactory because it causes severe distortion, vignetting, and illuminated areas with inhomogeneous brightness values distributed over the illumination field.
DE 40 28 605 C2 and its family member U.S. Pat. No. 5,126,877 present a known illumination device. An even earlier illumination device, functioning well per se, was already being commercialized in 1985 by the Applicant""s predecessor under the name xe2x80x9c0xc2x0 illumination optical systemxe2x80x9d (cf. brochure M1 668d-X.85, October 1985, of Wild Heerbrugg AG). In the xe2x80x9c0xc2x0 illumination optical system,xe2x80x9d it is possible, by rotating a disk, to add selectably, to a standard illumination at a small angle to the principal axis, a xe2x80x9c0xc2x0 illuminationxe2x80x9d which reduces the light flux of the standard illumination in proportion to its own increase in light flux. Theoretically, it is possible in this context to control the light flux distribution.
Although this known configuration is well-established, a great deal of effort was nevertheless devoted to finding newer approaches that did not involve light flux distribution, i.e. in which quantities of light flux are not subtracted from the one type of light flux in favor of the other light flux type. One such approach is recited in the German and U.S. documents referenced above.
A much more recent known configuration is described in JP-A-9-105866. Somewhat comparable to the early xe2x80x9c0xc2x0 illuminationxe2x80x9d configuration of the Applicant""s predecessor, here there is located under a first prism a second prism that has two mirror surfaces but is not rotatable about the principal axis. This configuration results in a fundamentally constant light flux distribution between the 0xc2x0 light flux portion and the greater light flux component that is always incident at a small angle; an overall reduction in light flux is possible by way of a slide-in stop in the principal beam path of the illumination optical system.
The problems of the prior art, including severe distortion, vignetting, and illuminated areas with inhomogeneous brightness values distributed over the illumination field, are eliminated by the invention by the fact that now, instead of an opaque stop, a stop with low light transmittance is used. A stop of this kind can be a neutral color filter, an aperture stop, a grid stop, or the like. According to a development of this invention, the light-transmitting areas of the stops could also be equipped with optical elements, thus resulting in a scattering of the light that, if necessary, illuminates the surgical field even beyond the illuminated area that has hitherto been standard. Instead of or in addition to such optical elements, markings such as, for example, crosshairs or the like could also be imaged in the illuminated field.
The user is thus given not only good perception of the surgical field but also, albeit only faintly, a view of, for example, surgical instruments introduced from the side and/or an additional indication concerning markings.
The stop can be arranged in front of either the light entry surfaces or the light exit surfaces of the light distribution and deflection apparatus.
The invention is not limited to these stops as recited, however, but rather can be equipped with any known or novel light regulation apparatus without losing its essence, namely the partially darkening configuration of the light beam at a small angle.
A particular embodiment and optionally an alternative to that described earlier, which can advantageously be utilized alternatively or also in combination and if necessary moreover results in an improved and even more symmetrical illumination, is characterized in that the stop is configured as a partially transparent mirror surface that deflects some of the beams emerging from the light distribution and deflection apparatus back toward the light source. With this configuration, when the one region is darkened, light can additionally be made available for the other, with no change in the output of the light source.
Independently of or in addition to the light flux control system, according to the present invention a light color control system can also be provided, such as color selection filter.